By John O'Brien

SINGAPORE (Reuters) - Angelique Kerber continued her relentless march towards a maiden WTA Finals crown with a comprehensive 6-2 6-1 victory over defending champion Agnieszka Radwanska on Saturday to set up a title showdown against Dominika Cibulkova.

The German enjoyed a breakthrough campaign with victories at the Australian and U.S. Opens to usurp Serena Williams at the top of the world rankings and after another dominant display, she will be favoured to cap her season with the Singapore title on Sunday.

"I was trying to be focused on every single point because playing against her is so tough, so I just made sure I played my game and was aggressive," Kerber said. "It's amazing to think that I will be in the final in Singapore."

Both players are renowned for their exemplary defense and supreme athleticism but, with serving not considered their strongest suit, it was hardly surprising to see the contest start with three straight breaks in favor of the German.

Kerber gave her Polish opponent no free points, got everything back and forced Radwanska into playing an extra shot on every rally, the constant pressure leading to another break in the seventh game, enough for the German to claim the opener.

Radwanska struggled to come up with any answers as the alarmingly consistent Kerber ran away with the contest against her dispirited opponent with four more breaks of serve.

In the first semi-final, Cibulkova continued her dream debut at the elite eight-woman event with a thrilling 1-6 7-6(2) 6-4 victory over Russian Svetlana Kuznetsova in an absorbing encounter.

INTENSITY LEVELS

The 27-year-old Slovakian, who had won their last five encounters, enjoyed a bright opening and threatened on Kuznetsova's first service game but some booming forehands bailed out the Russian, who edged ahead when she broke in the third game.

Kuznetsova was now firing on all cylinders, pushing Cibulkova all around the court and forcing her into errors and the rampant Russian secured two more breaks to complete a run of six straight games to wrap up the opener.

Cibulkova responded by stepping up her intensity levels in the second set and, as the tension mounted, neither player was capable of holding serve and four consecutive breaks from the ninth game sent it to a tiebreaker.

Cibulkova maintained her aggression in the tiebreak, sprinting 6-2 ahead as Kuznetsova struggled to keep pace and the Slovakian sent the contest into a decider when she rifled a backhand winner past her static opponent.

The third set was punctuated by several swings in momentum before Cibulkova followed up a gutsy hold from 15-40 in the ninth game to seal victory with another break.

"This is my first time here and it's one of my dreams come true, just incredible," world number eight Cibulkova said.

The final is a rematch of their opening round-robin match last Sunday in which Kerber beat the Slovakian 7–6(5) 2–6 6–3, the only contest of the week when the German lost a set.

(Editing by Clare Fallon)